Process for the production of carbon disulphide



Patented Feb. 1, 1938 UNITED STATES PATENT OFFICE PROCESS FOR THE PRODUCTKON OF CAR- BON DISULPHIDE ration of Great Britain No Drawing. Application February 10, 1937, Se-

rial No. 125,156. 1936 9 Claims.

This invention relates to an improved process for the manufacture of carbon disulphide.

The usual process for the manufacture of carbon disulphide involves the reaction between elemental sulphur and carbon. On a commercial scale this reaction is generally effected at temperatures in the neighborhood of 900 to 1000 C., the sulphur in the form of vapor being passed through a bed of the glowing carbon. Many proposals have been made as to the type of carbon which may be used. For instance, it has been suggested that brown coal, anthracite and coke can be used in the process. Wood charcoal of selected qualities is the only form of carbon which has been employed to any extent in commercial practice.

This invention has for an object the preparation of carbon bisulphide. A further object is the preparation of carbon bisulphide from a cheap and readily available source of carbon. A still further object is the preparation of carbon bisulphide of a good quality in commercial quantities. A still further object is a general advance of the art. Other objects will appear hereinafter.

These objects are accomplished by the following invention wherein sulphur in vapor form is passed through a bed of glowing carbon which has been prepared by carbonizing coal at a temperature between about 500 C. andabout 600 C. The carbon material may be reacted with sulphur immediately after the carbonization treatment or any time after. In the preferred embodiment of the invention the carbonized coal is subjected to aheat treatment at an elevated temperature in the substantial absence of air for a few hours and subsequently reacted with sulphur vapors.

The present invention is based on the observation that by the carbonization of coal at temperatures of the order of 500 to 600 C., a form of carbon is obtained suitable for reaction with sulphur vapor in the manufacture of carbon disulphide. This is surprising in view of the lack of success in the working of the prior proposals on a commercial scale. At the same time, care must be taken in the selection of the coal for carbonization. The various properties which are to be taken into consideration in this connection include ash content, carbon content, and eaking properties.

In connection with the ash content it is preferable, though not absolutely essential, that the material be of low ash content in order that possible mechanical difilculties may be avoided In Great Britain January 3,

in carrying out the reaction. Therefore, it is preferred that the coal before carbonization should be of low ash content. The carbon content of the initial coal is not critical but preferably it should be of low rank. That is to say, the carbon content should be relatively low in the neighborhood of to 82% calculated on the dry ashless basis. At the same time comparatively good results may be obtained when using material from the carbonization of coal of somewhat higher and somewhat lower carbon content. On the other hand, it is essential that the coal submitted to the carbonization process must not be readily fusible, it must be non-caking and probably should contain a high proportion of vitrain.

The conditions under which the carbonization is conducted must be carefully controlled, in order that the material produced may be suitable for successful large scale operation. This latter point is strikingly illustrated by trials which have been carried out on batches of washed coals. Average lots of a number of coals of the type above specified were carbonized at temperatures of 400, 500, 600 and 700 C., for periods of 1, 1.5, 3 and 5 hours in each case. Each lot of coke obtained from these carbonization runs was examined separately, when it was observed that only the cokes produced at temperatures of 500 and 600 C. were suitable for carbon disulphide manufacture commercially. Even with these materials there were differences which were apparently dependent on the duration of carbonization. Thus the cokes resulting from the treatments carried out for 1, 1.5. and 3 hours reacted at rates which were substantially the same as those observed with wood charcoal normally used, whereas carbonization for a period of 5 hours gave a material distinctly less reactive. With regard to the other temperatures we found that the use of 400 C. was inefiective for the production of a suitable coke, while the material formed at a temperature of 700 C. was distinctly less reactive than those produced at a temperature between about 500 C. and. about 600 C. This temperature range appears to be quite critical for the production of a suitable form of coal carbon for the reaction with sulphur, as We have found that a variation of much above 20 C. on either side furnishes a product which is markedly inferior.

Carbon produced in the manner described above is, when examined visually, characteristically different from coal carbon produced by normal coking processes and which is unsuitable for carbon disulphide manufacture. Whereas an unreactive coke has a silvery-grey appearance, the material used according to the present invention is quite black. Although not conclusive, this property enables a preliminary estimate to be made of the suitability of coal carbon for the reaction. Another property by which the carbon may be evaluated for the sulphur reaction is the rate at which it reacts with oxygen. Suitable carbons burn rapidly when heated in a flame in air as compared with a slow burning rate of unreactive carbons.

The reaction between the carbon and the sulphur for the production of carbon disulphide is carried out in the normal manner, for example, by charging the carbon into a vertical retort and passingsulphur'vapor through the glowing mass while maintaining a temperature of about 900 to 1000 C.

It is possible to use directly in this reaction the carbon produced by the carbonization of coal at 500 to 600 C. without any intermediate treatment. We find, however, that such carbon contains an appreciable content of combined hydrogen, a large proportion of which reacts with sulphur to form hydrogen sulphide during the manufacture of the carbon disulphide. This obviously reduces the efficiency of the process and in any case increases the equipment necessary for the treatment of the effluent gas from the process. Accordingly, we find it desirable to submit the coal carbon to a heat treatment shortly before it is passed into the carbon disulphide retort. This heat treatment may be carried out in the substantial absence of air in any convenient form of apparatus and con;- sists merely in heating the carbon to about 600 C. to about 800 C., and maintaining this temper-' ature for some hours. In this heat treatment some lowering of the reactivity takes place, but this is more than offset by theresulting gain in the general efiiciency of the carbon disulphide production. At the same time, however, it is necessary to avoid the use of temperatures materially higher than the above. If too high temperatures are used, the rate of the reaction between the sulphur and the carbon becomes too low for eflicient commercial production.

From a study of the above specification, the advantages of the above invention will be readily apparent. The chief advantage of the invention lies in the fact that an initial raw material which is inexpensive compared with wood charcoal becomes readily available for the production of carbon disulphide. Other advantages reside in the fact that carbon disulphide may be easily prepared in commercial quantities and in high quality.

As many apparently widely different embodiments of this invention may be .made without departing from the spirit and scope thereof, it is to be understood that this invention is not to be disulphide by reacting carbon and sulphur in known manner, characterized by the fact that the carbon used has been obtained by carbon izing coal between the temperatures of approximately 500 C. and approximately 600 C., for a period of 1 to 3 hours.

2. The process according to claim 1 further characterized by the fact that the carbon subsequent to the carbonization and prior to the reaction with sulphur has been submitted to a heat treatment'in the neighborhood of 700 C.

3. The process for the manufacture of carbon disulphide which comprises carbonizing a noncaking coal preferably of low ash content and relatively low carbon content at a temperature of approximately 500 to 600 C., for a period of 1 to 3 hours, and reacting the carbon thus obtained with sulphur.

4. The process according to claim 3 in which the carbon is submitted to a heat treatment subsequent to a carbonization process and prior to the reaction with sulphur.

5. The process of preparing carbon disulphide which comprises passing sulphur vapors over a bed of carbon material which has been prepared by carbonizing coal at a temperature between about 500 C. and about 600 C., for a periodof 1 to 3 hours. 7 q

6. The process of preparing carbon disulphide which comprises carbonizing coal at a'temperature between about 500C. and about'600 C. for a period of 1 to 3 hours, and then passing sulphur vapors over a bed .of such material maintained at an elevated temperature.

7. The process of preparing carbon disulphide which comprises carbonizing coal of low ash content and low carbon content at a temperature between about 500 C. and about 600 C. for a periodof 1 to 3 hours, heating the carbonized product to a temperature of about 600 to 800 C., and then passing sulphur vapors over theheat treated product which is maintained at an elevated temperature. r

8. The process according to claim 7 wherein the heat treated product is maintained at a temperature of about 900 to 1000 C.

9. The process of preparing carbon disulphide which comprises carbonizing coal of low ash content and having a carbon content of about to 82% calculated on the dry ashless basis at a temperature between about 500 to 600 C. for a period of from 1 to .3 hours, heating the carbonized product to a temperature of about 600 C. to 800 C. and then passing sulphur vapors over the heat treated product which is maintained at a temperature of about 900 to 1000 C.

JOHN PHILIP BAXTER. LESLIE JAMES BURRAGE. 

